Roller conveyors are used to transport goods carriers such as e.g. pallets. In the automobile industry they are often used to transfer vehicle bodies or parts of vehicle bodies between individual processing stations. The vehicle bodies are in said case fastened on so-called skids. This term is used for transport racks that have two mutually parallel skid runners. During the conveying operation the skid runners rest on rollers of the roller conveyor, which are disposed successively in conveying direction along two tracks. When the rollers are set in rotation, the skid with the vehicle body fastened thereon is fed in conveying direction, wherein it is sufficient to provide only some of the rollers with a rotary drive.
Known roller conveyors of the initially described type, such as are currently known from the market, are composed of individual roller conveyor modules, which contain a plurality of driven rollers and in each case a single electric drive motor. The drive motor is disposed as a rule between the two parallel tracks, which are composed of roller rails, in which the rollers are accommodated. Mostly, the torque generated by the drive motor is distributed by belts to the driven rollers of one of the two roller rails. These rollers are connected by axles rigidly to the rollers on the other roller rail.
In these known roller conveyors, therefore, the number of drive motors is lower than the number of driven rollers.
The voltage used to operate the drive motors is identical to the system voltage that is available in each case and is therefore generally between approximately 200 V and approximately 600 V. Because of the relatively high operating voltage it is necessary to take considerable safety measures, this being associated with costs. Costs are further increased by the fact that the semiconductor components, to which the high operating voltage is to be applied, are relatively expensive and have a relatively high loss factor.
The present invention is provided to solve these and other problems.